The present invention relates generally to rear-projection television (RPTV) systems, computer monitor and portable data display systems, and more particularly to electronic image projector engines. More particularly, the present invention relates to projection engines which enable the use of reflective liquid-crystal-on-silicon semiconductor light valve imaging devices, commonly referred to as xe2x80x98liquid-crystal-on-silicon imagers.xe2x80x99
Until recently, demand for electronic image projectors has been limited to business and professional environments where the high cost and complexity of prior art image projection systems is a lesser limiting factor in their applicability. The large number of optical components, the requirement to maintain accurate positioning in the projector engine assembly during use, and the high cost of prior art electro-optic xe2x80x98imagerxe2x80x99 devices (e.g., TFT-LCD, DMD, ILA, etc.) limits the marketability of products using such prior art technologies. Moreover, prior art projection engines inefficiently use the optical information provided by the imager.
Recently, image content with dramatically higher resolutions has emerged in the consumer television and computer display environments, bringing higher demand for projected image systems. However, prior art projected image systems cannot display these high-resolution images with a price that consumers are willing to pay. Moreover, prior art projected image systems do even not provide performance levels that justify their high cost. Thus, there is a need to reduce the complexity and cost of projected image system technology while improving manufacturability, reliability, image quality, system lifetime, heat production, color purity, lamp efficiency and contamination resistance.
The need for large, high resolution display devices is becoming more important because the United States and other countries are in the process of shifting from an analog, low resolution television delivery system, to a digital, high resolution delivery system, sometimes referred to as xe2x80x9chigh-definition televisionxe2x80x9d, or xe2x80x9cHDTVxe2x80x9d. There is also a need for larger and higher-resolution computer monitors. In terms of resolution, the current television delivery system in North America, known as NTSC (this format was developed by the National Television Standards Committee-hence the format has been named NTSC) has addressable resolution of approximately 425 by 565 pixels. Pixel density is most common method of expressing the resolution of a display device. A xe2x80x98pixelxe2x80x99 is the basic xe2x80x98picture elementxe2x80x99 of an image (sometimes referred to as xe2x80x98pelsxe2x80x99). The term pixel usually applies to the quantification of electronic images, which are composed of an array of pixels that each define a tiny portion of the image. This array of image picture elements is usually specified by a vertical number and a horizontal number, the product of which is the total number of pixels. Thus, the NTSC picture can provide, at best, approximately 240,125 total pixels.
For bandwidth conservation reasons, the typical cable television signal fed to most U.S. households arrives with even less resolution, approximately 350 by 466 pixels (163,100 total pixels). While there are as many as eighteen different formats proposed for digital television, there are three different resolutions likely to be established as final standards and used by terrestrial broadcast, direct broadcast satellite and cable companies. These formats are base digital television, 480 by 640 pixels (307,200 total pixels), low HDTV, 720xc3x971280 pixels (921,600 total pixels), and high (or full) HDTV, 1080 by 1920 pixels (2,073,600 total pixels). Thus, it is seen that a television capable of displaying full HDTV resolution must have the ability to display nearly nine times as much picture information (i.e., nearly nine times as many pixels) as current NTSC broadcasts require. Moreover, even lower resolution digital television formats greatly exceed the cost-per-pixel capabilities of the projection-CRT.
Prior art projection image technologies are not capable of efficiently displaying full HDTV resolution at low cost. By far the most popular large screen television system is the rear projection television, known as RPTV. A typical RPTV uses three cathode ray tubes that project picture data onto the rear of a transmission screen. The screen then distributes the picture data into an image viewing field, within which the viewer can see it. Demand for inexpensive televisions and computer monitors having large image sizes and high resolution has prompted leading semiconductor manufacturers to develop reflective liquid-crystal-on-silicon semiconductor imaging device components. This electro-optic component, often referred to as an xe2x80x98imager,xe2x80x99 is essentially an electronic device constructed to operate as a reflective light valve. The reflective liquid-crystal-on-silicon light valve is comprised of a semiconductor integrated circuit on a single piece of silicon, similar to a DRAM or other such electronic memory device. Its surface contains the electronic image elements, i.e. its pixels, in regular array within its active area. The integrated circuit is transformed into an electro-optic device through established methods by plating its surface with a reflective mirror metal or suitable dielectric thin-film stack such that light incident upon it is reflected at high efficiency amidst the electric fields created at the surface of the device. Using methods well known in the liquid crystal display trade, a twisted-nematic (TN) or other such liquid crystal cell is bonded atop the surface of the silicon die in close proximity. When this combination is illuminated with polarized light, the resulting construction acts in effect as a reflective light polarization modulator wherein each picture element on the surface of the integrated circuit can be separately controlled electronically.
Reflective liquid-crystal-on-silicon light valve component devices are now readily available from a number of manufacturers. Their development has been driven by the simple fact that they are less expensive to manufacture in high volumes than thin-film transistor (TFT) or digital-micro-mirror (DMD) imager components used in the architectures of established solid-state projection engines. They are also capable of much higher market applicability since their manufacture does not require customized equipment, unlike TFT and DMD imagers, which have experienced only narrow demand in business and professional environments. Instead, reflective liquid-crystal-on-silicon imager devices are manufactured on existing xe2x80x98memory chipxe2x80x99 process lines.
For reflective liquid-crystal-on-silicon light valve imagers to be useful in televisions and computer monitors having larger viewing area and higher resolution, a projection engine optical architecture having high performance and low cost is necessary. An image xe2x80x98projection enginexe2x80x99 is a term used in the trade to denote the essential assembly within a projection system, usually taken to mean all components from the lamp to the projection lens. None of the prior art projection engine optical architectures can provide either high performance or low cost when using liquid-crystal-on-silicon light valve imagers. The various embodiments of the present invention show television or computer monitor using an engine architecture capable of significantly higher resolution than the resolution limits of projection cathode ray tube technology at cost demands of the consumer user.
The transformation of light collected from a bright lamp into image luminance on a screen is a fundamental purpose of image projection engines. The lamp used in an RPTV or monitor is typically an arc lamp, which emits white light in all directions. Geometrically organizing and redirecting this randomly directed white light into uniformly directional and focused light, thereby creating an image, is the purpose of a projector engine.
Light collection in optics is quantified by either f/# or numerical aperture, yet both quantities describe the angular extent of a particular cone of light and are directly related. The f/# describes the angular extent of a light cone by the ratio of the length of the cone to its diameter:
f/#=focal length/diameter
whereas numerical aperture, N.A., directly describes the angle of the cone of light within which all light is contained:
N.A.=n*sin xcex8
where n is the index of refraction of the optical medium within which the cone resides, and xcex8 is the angle created by the margins of the contained light cone and the optical axis. Numerical aperture can be easily converted to f/# by the relation:
f/#=1/(2*N.A.)
In the collection stage of the projection engine, numerical aperture and f/# quantify the geometrical directionality advantage the reflector can produce over the random directionality natural to the lamp""s emission. The absolute values (i.e., the numerical value) of numerical aperture and f/# are essentially inversely proportional to one another, yet both describe the same geometric containment within a light cone. Large N.A. corresponds to large cone angle, and large f/# corresponds to small cone angle.
Light from the lamp is emitted in all directions, so its collection by a reflector or lens or other such collection means transforms this emission from a maximum solid angle directionality of 4xcfx80 steradians into a cone of specific numerical aperture. This is referred to as the xe2x80x9ccollection stagexe2x80x9d of the optical architecture and is critical to engine performance since the projection engine can only use light contained within this collected numerical aperture. Any light that is lost (i.e., not collected), results in lost image brightness. Subsequent to the collection stage is the xe2x80x9cillumination stage,xe2x80x9d where the cone of light from the collection stage is transformed to a yet narrower and more practical cone of light, which is then focused to illuminate the reflective liquid-crystal-on-silicon imager residing in an xe2x80x9cimaging stage.xe2x80x9d It is within the imaging stage where the light is spectrally separated, modulated, and spectrally combined upon exit of the imaging stage through the projection lens and out to the screen.
A key aspect of the invention is an improvement in the performance of the polarization components within the imaging stage, including the reflective liquid-crystal-on-silicon imager, attained when the cone of light focused onto the active area of the imager be of a special angular order specified in optics as a xe2x80x98telecentricxe2x80x99 focus. A telecentric focus is one where each point at the focus on the area of the imager is comprised of identical angular bundles that are centered symmetrically about the perpendicular axis. The purpose of presenting telecentric illumination to the imaging stage is to: (1) assure that each pixel locale on the imager device is illuminated by a cone of light that is spatially identical in every way to the cone of light illuminating every other pixel locale; and to (2) assure that each locale on the hypotenuse of the polarization beamsplitter cube components within the engine are illuminated by a cone of light that is spatially identical in every way to the cone of light illuminating every other locale on the hypotenuse. This process significantly improves the polarization performance of these components across the desired spectral waveband.
A primary property of reflective liquid-crystal-on-silicon imagers is the polarization of light. The degree to which polarization is processed and transformed within the projection engine is of paramount importance to its total image performance. Polarization is commonly resolved into two opposite spatial components, xe2x80x9cPxe2x80x9d and xe2x80x9cSxe2x80x9d. A vector quantity pertinent to this polarization property is the xe2x80x9cpolarization statexe2x80x9d of a particular beam of light. The polarization states of interest are xe2x80x9cP-polarizationxe2x80x9d, which is the alignment of the polarization vector with the electric field vector of the light waves, and xe2x80x9cS-polarizationxe2x80x9d, which is the polarization vector perpendicular to the electric field vector of the light waves. As used herein, polarization logic means that a polarization vector pointing in any direction of the compass about the optical axis can be resolved into its two constituent components in the S direction or the P direction. The quality of the contrast in the engine polarization states is directly converted into luminance contrast in the image, which the viewer sees as the full black and full white states of the image. Thus, high contrast between P-polarization and S-polarization is necessary for high image quality.
Prior art projection engine architecture is not appropriate for display systems using reflective light valve imager devices. The reason for this is that liquid-crystal-on-silicon light valves have reflective geometry characteristics and polarization dependence characteristics, among others, that are significantly different than TFT transmission-LCD or reflective DMD imaging devices. Prior art engines simply do not work well with liquid-crystal-on-silicon light valves because they are trying to create an image from an electro-optic device that is significantly different in character.
All projection engine architectures must perform the following functions. The engine must collect, condense and condition raw bulb light emission for illumination of the imager devices. Then, the engine must separate the white light from the lamp into three primary colors, polarize each color appropriately for presentation to three reflective liquid-crystal-on-silicon light valve modulators. The engine must then analyze polarization of the modulated primary images after reflection from the imagers, and then combine the primary colors through a projection lens that focuses the combined image onto the screen.
Prior art engines are not ideally suited for use with reflective liquid-crystal-on-silicon light valve modulators. For example, in U.S. Pat. No. 4,983,032 to Van Den Brandt (xe2x80x9cthe Van Den Brandt ""032 patentxe2x80x9d), U.S. Pat. No. 5,028,121 to Baur et al (xe2x80x9cthe Baur ""121 patentxe2x80x9d), U.S. Pat. No. 5,577,826 to Kasama et al (xe2x80x9cthe Kasama ""826 patentxe2x80x9d) describe various projection engines established for use with reflective imaging components. None of these prior art engines suggest that they can be used specifically with reflective liquid-crystal-on-silicon semiconductor devices, and each has deleterious conceptual issues and efficacy concerns specific or peculiar to them. Indeed, as mentioned above, engines designed for use with other reflective imagers such as DMD (Digital Micro-Mirror Device), PDLC (Polymer Dispersed Liquid Crystal), FMLC (Ferro-Magnetic Liquid Crystal) are not likely to be useful as an engine for a display device using a liquid-crystal-on-silicon semiconductor imager. Moreover, none of these prior art references take into account real world problems, the most important of which is the waste light created by the various optical elements they use. This will be discussed in more detail below.
Referring specifically to the Van Den Brandt ""032 patent, the first limitation is the dichroic plates that separate and combine its color spectra. These dichroic plates are set at an angle relative to both incident and reflected beams passing through them. Characteristic to reflective liquid-crystal-on-silicon light valve imager is that its incident and reflected beams are of opposite polarization, allowing for it to function as a light valve modulator. The imager reflection encodes the image onto the incident beams by rotating, or xe2x80x9ctwistingxe2x80x9d the reflected return polarization a maximum of ninety degrees. The quality of the spectral responses of the dichroic separation layers positioned at an angle to both incident and return beams is greatly reduced when the angled dichroic layers process color in separate and opposite polarization states. The result of this angular dichroic configuration is a shift of the dichroic transmission spectra between incident and reflected beams, causing irreconcilable chromatic waste light and reduction of polarization purity which contaminates the image quality, resulting in reduction of throughput efficiency, color purity and image contrast.
A second limitation to the Van Den Brandt ""032 patent is that it is based on xe2x80x9coff-axis illumination,xe2x80x9d such that light falls incident on the reflective imager from a principle angle other than zero degrees. This causes the liquid crystal reflective imager contrast and color luminance uniformity performance to be reduced with the angle of incidence. Moreover, off-axis illumination requires larger, costlier optical components along with precise mechanical positioning of the components in the assembled engine, which is also costly as well as inherently problematical.
A third limitation of the architecture disclosed in the Van Den Brandt ""032 patent is its excessively long optical path length that a projector utilizing this engine must have. This longer path length from imager to projection lens adversely affects the cost and performance of the projection lens, and adversely affects the xe2x80x98etendu pointxe2x80x99 of the system. Etendu, described in detail below, is a measurement of allowable angular and brightness transformations governed by fundamental thermodynamic effects.
A fourth limitation of the architecture disclosed in the Van Den Brandt ""032 patent is that it requires accurate positioning of its optical components in a solid assembly structure to obtain a properly aligned image on the screen. This increases manufacturing cost and lowers long term reliability. In addition, since the components are in air, a fifth limitation in real engine embodiments of this architecture is the need to effectively seal the engine volume from particle contaminants visible in the projected image as optical surfaces collect dust and vapor contamination. Finally, the Van Den Brandt ""032 patent completely ignores the waste light created by its various optical components. Failure to compensate for this waste light renders the teachings of Van Den Brandt ""032 patent of little value.
Therefore while the Van Den Brandt ""032 patent discloses an engine for reflective imagers, it has many disadvantages in performance, cost, efficiency and viability.
An advantage of the engine described in Kasama ""826 over that described in Van Den Brandt 032 is its xe2x80x9cretroreflectivexe2x80x9d approach. Retroreflection does offer certain advantages over an off-axis system. Retroreflection is the optical term used to describe zero degree incidence to a reflective surface such that the incident and reflected beams lie along the same path and are separated only by their opposite direction. The light path in such an instance, travels along a retroreflective axis. Reflective liquid-crystal-on-silicon imager devices are desirably illuminated at zero degrees incidence to maximize contrast and luminance uniformity performance as well as to require smaller components and more compact engine volumes. The sharing of the optical path between incident and reflected beams allows a single polarization beamsplitter cube to both polarize and analyze the sent and returned light beams, provided the design concept establishes means to remove or redeem polarization waste, which the Kasama ""826 does not suggest. The failure to of the Kasama ""826 patent to teach any method of removing or rejecting the color and polarization waste render its teachings of little value.
The other limitations of the engine in the Kasama ""826 patent are similar to those of the Van Den Brandt ""032 patent. To separate and combine primary colors, a dichroic plate is used at oblique angles to both incident and return beams possessed of opposite polarizations. This reduces throughput efficiency, color purity and contrast performance. Another similar limitation of the engine of the Kasama ""826 patent is the need to accurately position optical components in air, which decreases stability and increases the likelihood of contamination. A third limitation is the long optical path, or back focal length, from imager to projection lens, reducing projection lens performance as well as mandating less efficient collimated incident light.
A fourth limitation of the Kasama ""826 patent is the inability of the design to deliver pure polarization states between incident and retroreflected beams. Since the beam reflected from each imager is rotated a maximum of ninety degrees in polarization state relative to the incident beam, each optical component in the architecture operates in both polarizations. This renders it impossible to insert subsequent polarization components to trim or xe2x80x98cleanxe2x80x99 either state without adversely affecting the other polarization state. This results in a reduction of contrast performance. Due to the physics of polarization beamsplitter cubes, the single polarization beamsplitter cube shown in the design does not produce high quality polarization equally in both P and S states. The quality of the contrast in the engine polarization states is directly converted into luminance contrast in the image, which the viewer sees as the full black and full white states of the image.
Finally, neither the Kasama ""826 patent nor the Van Den Brandt ""032 patent can be effectively manufactured to operate at high xe2x80x9ccollection speed.xe2x80x9d Collection speed refers to optical systems that do not attempt to collimate light from the lamp into small angles, but rather condenses it into a large angle range of distinct focus and numerical aperture. Collection speed is profoundly related to the throughput efficiency of the projection engine. The reason for this is that, at higher speed, light from the lamp can be collected and transferred through the engine at higher efficiency. Efficiency is improved in high-speed systems because the engine can operate closer to its xe2x80x98etendu pointxe2x80x99. Etendu is the optical term used to describe the maximum allowable light that can be geometrically directed from the lamp onto the imager and will be discussed in more detail below.
An advantage of the Baur ""121 patent over the other described patents is its solid, cemented prism assembly with reflective imager devices attached. This removes the need for an accurate mechanical structure in the engine assembly to secure its components during operation and seals the critical optical surfaces against contamination. The permanently attached imagers bonded onto a solid prism subassembly require alignment and positioning only a single time during its manufacture and not in the engine product itself. This frees the architecture from requiring positioning and sealing apparatus and hardware in its embodiments.
However, the projection system disclosed the Baur ""121 patent and other similar prior art systems have limitations in performance and viability. A first limitation of the architecture disclosed in the Baur ""121 patent is the reliance of dichroic color separation and combining layers situated at steep angles to both incident and reflected beams of opposite polarization. In fact, this condition is worsened in the Baur ""121 patent""s architecture because these dichroic layers are immersed in glass at 45xc2x0, further widening the spectral disparity in their response when compared to the same dichroic surface in air. Baur discloses an xe2x80x9cX-cubexe2x80x9d configuration where two dichroic planar layers of differing spectra intersect in an xe2x80x98Xxe2x80x99 shape within a glass cube. This component is commonly found in projectors with transmissive TFT imagers, where color separation and combining functions are isolated and not subjected to beams of opposite polarizations. However, their use for reflective liquid-crystal-on-silicon imagers, which characteristically prefer separation and combining functions in a single set of color components operating in retroreflection, requires that the immersed dichroic layers operate in both polarizations. This process, especially in the immersed dichroic embodiment disclosed in the Baur ""121 patent, produces high levels of undesirable waste light, which, as discussed, reduces throughput, image contrast and produces color leakage (i.e., mixing) between the primary colors. It is for this reason that the architecture of the Baur ""121 patent requires nearly collimated light rather than illuminating the architecture at higher optical speed, where the deleterious effects of immersed angular dichroic layers are exacerbated.
A second limitation of the Baur ""121 patent""s architecture is the fact that it requires either the use of six reflective imagers rather than three, or else a fifty percent sacrifice in engine light throughput efficiency. Both of these requirements are insufficient to achieve satisfactory basic or further functionality requirements. For example, the six reflective imagers mandated by the design to account for what would otherwise be a loss of half the usable light, is arranged with two reflective imagers per primary color channel rather than simply one. This not only doubles the cost of the electro-optic components in the engine, but also adds additional manufacturing complexity. Converging six active pixel areas during manufacture is considerably more elaborate than aligning only three active pixel areas.
A third limitation of the Baur ""121 patent""s architecture relates to its fundamental structure, which mandates a single polarization component, a polarization beamsplitter cube. Since beams of both polarizations share the retroreflective paths, polarization trim or clean up components cannot be used to improve the design""s limiting polarization contrast. This places an unrealistically high demand on the quality of the polarization in both states attainable from real polarization beamsplitter components in white light and especially at higher optical speeds. Thus, the Baur ""121 patent""s architecture cannot produce acceptable basic functionality as well as any advances in further functionality.
Thus, there is a need for a low cost, high performance, optical engine for use in rear projection television and computer monitor applications having improved performance and lower cost than those of the prior art.
A new type of projection engine architecture for use in projection television, computer monitor or data displays of either front or rear projection is disclosed.
In a first aspect of the present invention, a method for creating an image in a projected image device comprising the steps of providing a first polarization telecentric white light beam, splitting the first polarization telecentric white light beam into a first polarization telecentric green light beam and a first polarization telecentric magenta light beam. The first polarization telecentric green light beam is directed onto a first liquid-crystal-on-silicon semiconductor light valve imaging device such that the first liquid-crystal-on-silicon semiconductor light valve imaging device reflects a second polarization green light beam containing pixel data. The second polarization green light beam containing pixel data is switched into a first polarization green light beam containing pixel data. The first polarization green light beam containing pixel data is directed along an output axis while substantially all green waste polarization light is directed along an axis separate from the output axis. The first polarization red component of the first polarization telecentric magenta light beam is switched into a second polarization red light beam. The second polarization red light beam is directed onto a second liquid-crystal-on-silicon semiconductor light valve imaging device such that the second liquid-crystal-on-silicon semiconductor light valve imaging device reflects a first polarization red light beam containing pixel data. The first polarization red light beam containing pixel data is directed along an output axis while substantially all red waste polarization light is directed along an axis separate from the output axis. The first polarization red light beam containing pixel data is switched into a second polarization red light beam containing pixel data. The first polarization blue component of the magenta beam is directed onto a third liquid-crystal-on-silicon semiconductor light valve imaging device such that the third liquid-crystal-on-silicon semiconductor light valve imaging device reflects a second polarization blue light beam containing pixel data. The second polarization blue light beam containing pixel data is directed along an output axis while substantially all blue waste polarization light is directed along an axis separate from the output axis.
In another aspect of the present invention, the first polarization state is S-polarization while the second polarization state is P-polarization.
In another aspect of the present invention, an imaging structure for use in a projected imaging device is disclosed that comprises a color separation component that splits a first polarization white light beam into a first polarization green light beam and a first polarization magenta light beam. In preferred embodiments, the color separation component is dichroic mirror. The imaging structure also comprises a first polarizing beamsplitter cube positioned to receive the first polarization green light beam, a second polarizing beamsplitter cube positioned to receive the first polarization magenta light beam, and a third polarizing beamsplitter cube. The imaging structure of this aspect of the present invention also comprises a first liquid-crystal-on-silicon semiconductor light valve imaging device affixed to a first face of the first polarizing beamsplitter cube. A second liquid-crystal-on-silicon semiconductor light valve imaging device is affixed to a first face of the second polarizing beamsplitter cube. A third liquid-crystal-on-silicon semiconductor light valve imaging device affixed to a second face of the second polarizing beamsplitter cube. A first retarder is affixed to a second face of the first polarizing beamsplitter cube and a first face of the third polarizing beamsplitter cube. A second retarder is affixed to a third face of the second polarizing beamsplitter cube. The imaging structure also comprises a third retarder that is affixed to a fourth face of the second polarizing beamsplitter cube and a second face of the third polarizing beamsplitter cube.
In another aspect of the present invention, an imaging structure is disclosed which comprises a color separation component that splits a first polarization white light beam into a first polarization green light beam and a first polarization magenta light beam. A first polarizing beamsplitter cube is positioned to receive the first polarization green light beam. A first liquid-crystal-on-silicon semiconductor light valve imaging device affixed to a first face of the first polarizing beamsplitter cube. A first retarder is affixed to a second face of the first polarizing beamsplitter cube that is adapted to switch polarization state of green light. A second polarizing beamsplitter cube is positioned to receive the first polarization magenta light beam. A second retarder is affixed to a first face of the second polarizing beamsplitter cube which is adapted to switch polarization state of red light. A second liquid-crystal-on-silicon semiconductor light valve imaging device affixed to a second face of the second polarizing beamsplitter cube. A third liquid-crystal-on-silicon semiconductor light valve imaging device is affixed to a third face of the second polarizing beamsplitter cube. A third retarder is affixed to a fourth face of the second polarizing beamsplitter cube that is adapted to switch polarization state of red light. A third second polarizing beamsplitter cube is positioned such that a first face thereof is affixed to the first retarder and a second face thereof is affixed to the third retarder.
In another aspect of the present invention, an inventive compander for use in an electronic image projector engine that uses reflective imaging devices having a specified aspect ratio and specified surface area. The compander is adapted to receive a light beam having an illumination structure. The compander smoothes the illumination structure, de-circularizes the light beam, sets engine etendu point, transforms numerical aperture of the light beam to a predetermined numerical aperture, magnifies the light beam to create a light beam aperture having the specified aspect ratio and the specified surface area, and renders the light beam telecentric. The compander comprises an elongate member comprised of an optical material, and has an entrance face and an exit face. The exit face is oppositely opposed from the entrance face. The entrance face has a quadrilateral shape with a first aspect ratio and a first surface area. The exit face having a quadrilateral shape with a second aspect ratio and second surface area. The second surface area being greater than the first predetermined surface area. In an aspect of the present invention, the compander is such that the first aspect ratio and the second aspect ratio are substantially identical. In an aspect of the present invention, the compander is such that the second aspect ratio is substantially identical to the specified aspect ratio. In an aspect of the present invention, the compander is such that the optical material is glass. In an aspect of the present invention, the compander is such that the optical material is plastic. In an aspect of the present invention, the compander is an integral, one piece structure.
In another aspect of the present invention, an engine architecture for a projection device is disclosed that comprises a collection stage, an illumination stage and an imaging stage. In another aspect of the invention, an engine comprising a light source a reflector that collects and condenses light emitted by the light source into a first focus of light, and a mirror that redirects the first focus of light is disclosed. A compander positioned to receive the first focus of light that comprises an elongate member having an entrance face and an exit face oppositely opposed from the entrance face. The entrance face comprises a quadrilateral having a first aspect ratio while the exit face comprises a quadrilateral having a second aspect ratio. This compander outputs a telecentric light beam. A first polarizing beamsplitter cube for receipt of the telecentric light beam is oriented such that it outputs a telecentric light beam having a first polarization. A condenser receives the telecentric light beam having the first polarization state from the first polarizing beamsplitter cube and focuses this light beam along a first optical axis.
A dichroic mirror is disposed at a substantially forty-five degree angle with respect to the first optical axis that is adapted to split the light beam into a green light beam substantially along a second optical axis and a magenta light beam substantially along the first optical axis. The magenta beam has a red component and a blue component.
A prism assembly comprising a first dichroic trimming mirror is positioned substantially perpendicular to the second optical axis. A second polarization beamsplitter cube comprising a first beam splitting hypotenuse reflects the first polarization green light along a third optical axis and transmits second polarization green light along the second optical axis. A first reflective liquid-crystal-on-silicon semiconductor light valve imaging device is affixed to the second polarization beamsplitter cube and is substantially perpendicular to the third optical axis. The first reflective liquid-crystal-on-silicon semiconductor light valve imaging device reflects green light towards the first beam splitting hypotenuse along the third optical axis. The first beam splitting hypotenuse reflects the first polarization green light along the second optical axis and transmits second polarization green light along the first optical axis.
A first half-wave retarder is affixed to the second polarization beamsplitter cube and is substantially perpendicular to the third optical axis. A second dichroic trimming mirror is arranged substantially perpendicularly to the second optical axis. A second half-wave retarder is affixed to the second dichroic mirror and is substantially perpendicular to the first optical axis. The second half-wave retarder switches first polarization red light to the second polarization.
A third polarization beamsplitter cube comprising a second beam splitting hypotenuse which reflects first polarization light along a fourth optical axis and transmits second polarization light along the second optical axis. A second reflective liquid-crystal-on-silicon semiconductor light valve imaging device is affixed to the third polarization beamsplitter cube and being substantially perpendicular to the first optical axis. The second reflective liquid-crystal-on-silicon semiconductor light valve imaging device reflects red light towards the second beam splitting hypotenuse along the first optical axis. The second beam splitting hypotenuse reflects first polarization red light along the fourth optical axis and transmits second polarization red light along the first optical axis.
A third reflective liquid-crystal-on-silicon semiconductor light valve imaging device is affixed to the third polarization beamsplitter cube and is substantially perpendicular to the fourth optical axis. The third reflective liquid-crystal-on-silicon semiconductor light valve imaging device reflects blue light back towards the second beam splitting hypotenuse along the fourth optical axis. The second beam splitting hypotenuse reflects first polarization blue light along the first optical axis and transmits second polarization blue light along the fourth optical axis.
A third half-wave retarder is affixed to the third polarization beamsplitter cube and is substantially perpendicular to the fourth optical axis. The third half-wave retarder switching the first polarization red light to the second polarization. A fourth polarization beamsplitter cube is affixed to the first half-wave retarder and the third half-wave retarder such that the third optical axis is substantially perpendicular to the fourth optical axis. The fourth polarization beam splitter cube comprises a third beam splitting hypotenuse which reflects first polarization light along the third optical axis and transmits second polarization light along the fourth optical axis.
In another aspect of the present invention, the image projection engine apparatus is such that light beams having the first polarization are in an S-polarization state and light beams having the second polarization are in a P-polarization state.
In another aspect of the present invention, the image projection engine apparatus is such that first aspect ratio and the second aspect ratio are the same. In another aspect of the present invention, the image projection engine apparatus is such that the entrance face has smaller surface area than the exit face. In another aspect of the present invention, the image projection engine apparatus is such that the first imaging device, the second imaging device and the third imaging device are quadrilateral in shape and have a third aspect ratio. In another aspect of the present invention, the image projection engine apparatus is such that the third aspect ratio is equal to the second aspect ratio. In another aspect of the present invention, the image projection engine apparatus also includes a projection lens aligned along the fourth optical axis. In yet another aspect of the present invention, a rear projection television or computer monitor utilizing the engine is disclosed.
The construction and arrangement of the fundamental projection engine architecture according to the present invention provides many advantages over the prior art. One exemplary advantage is better image performance for liquid-crystal-on-silicon projection engines in all attributes of basic functionality. Luminous efficiency, contrast, luminance output, color uniformity and resolution are superior to existing architectures utilized in competing projector technologies of like classification. Another advantage provided are remedies for specific physical loss mechanisms unique to reflective liquid-crystal-on-silicon imaging. Another advantage of the present invention is substantially reduced costs, complexity and component count to embody or manufacture a quality engine design based on the architecture. Another advantage is high projected image performance with a minimum number of optical components. Another advantage is its very small optical components, enabling engine products substantially smaller in overall size than prior art projectors. Another advantage is high speed light collection. Yet another advantage is the transformation of numerical aperture in the illumination stage without relying on complex condenser lens systems. Another advantage is the inherent fundamental telecentricity in the illumination stage. Still another advantage is the remote positioning of the projection lamp to an ideal location for enclosed rear projection cabinets without sustaining attendant geometric efficacy losses. Yet another advantage is the inclusion of the primary polarizing PBS cube component in the illumination stage before the condenser lens, rather than the imaging stage after the condensing lens. Another advantage is a short back focal length (BFL) imaging stage, substantially reducing projection lens cost and manufacturability.
One advantage of an inventive aspect of the present invention is to provide an improved image projection engine architecture.
Another advantage of an inventive aspect of the present invention is to provide an improved projection engine.
Another advantage of an inventive aspect of the present invention is to provide an improved projection engine through a minimum number of components and significantly reduced complexity.
Another advantage of an inventive aspect of the present invention is to provide a rear-projection engine viable for use in consumer television, computer monitors, and broader, general use.
Another advantage of an inventive aspect of the present invention is to provide an improved cost-performance front-projection engine for commercial or business uses.
A further advantage of an inventive aspect of the present invention is to improve basic engine functionality such as efficiency and contrast performance.
Another advantage of an inventive aspect of the present invention is the elimination of dichroic components operating at oblique angles within a retroreflective imaging stage.
A further advantage of an inventive aspect of the present invention is to improve image quality performance by operating the primary color processing function in the magenta and green wavebands such that the subsequent red-blue color separation occurs in the vacant portion, or notch, of the magenta waveband.
Another advantage of an inventive aspect of the present invention is a simple illumination stage which delivers ideal geometrically constructed light to the imaging stage containing the reflective liquid-crystal-on-silicon imagers.
Still another advantage of an inventive aspect of the present invention is a solid, cemented imaging stage combination which eliminates mechanical positioning hardware in a product engine assembly.
Another advantage of an inventive aspect of the present invention is an engine imaging stage wherein waste light and rejected light caused by polarization and color separation losses are eliminated by specific means and implementations.
Another advantage of an inventive aspect of the present invention is imaging stage xe2x80x98exit portsxe2x80x99 within the imaging prism subassembly which remove waste light immediately after it is created in the imaging stage.
The above and other preferred features of the invention, including various novel details of implementation and combination of elements will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular methods and apparatus embodying the invention are shown by way of illustration only and not as limitations of the invention. As will be understood by those skilled in the art, the principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.